I have a late 2010 MBA 11", and I've been running into an issue where the backlight won't turn on when I open the lid. I can see (barely) that the screen is on, but I can't get the backlight to turn on. I have to close the lid (sometimes a few times), and eventually it'll come on.

I've had similar issues on a 2012 13in MBA running 10.8.2. At first I thought it just wasn't waking up and ended up powering it off and back on; but then I noticed it happen when there was sufficient daylight to see the screen, and realised it was the backlight.

It's only happened during or after a charge - opening the lid both when it's still plugged in and after removing the charger plug.

I've worked round it by closing and reopening the lid, as you say, or briefly pressing the Esc button to cancel & sleep again, then any key to re-awake.